The railway signalling

Railway signalling

Railway signalling is a system used to control railway traffic safely, essentially to prevent trains from colliding. Being guided by fixed rails, trains are uniquely susceptible to collision; furthermore, trains cannot stop quickly, and frequently operate at speeds that do not enable them to stop...

systems used across the majority of the United Kingdom

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 rail network use lineside signals to advise the driver of the status of the section of track ahead. Most lineside signals are in colour light form, but a significant number of semaphore signals remain on secondary lines.

The traditional British signal is the semaphore, comprising a mechanical arm that raises or lowers to indicate 'clear' (termed an "upper-quadrant" or "lower-quadrant" signal, respectively).